PHP实现截取字符串的通用方法

/**
  * 截取字符串
  * params $string 要截取的字符串
  * params $length: 保留长度（字符数）
  * params $dot: 多余部分显示
**/
function _cutstr($string, $length, $dot = ' ...') {
    if(strlen($string)         return $string;
    }
    $string = str_replace(array('&', '"', ''), array('&', '"', ''), $string);
    $strcut = '';
    $n = $tn = $noc = 0;
    while($n         $t = ord($string[$n]);
        if($t == 9 || $t == 10 || (32             $tn = 1; $n++; $noc++;
        } elseif(194             $tn = 2; $n += 2; $noc += 2;
        } elseif(224             $tn = 3; $n += 3; $noc += 2;
        } elseif(240             $tn = 4; $n += 4; $noc += 2;
        } elseif(248             $tn = 5; $n += 5; $noc += 2;
        } elseif($t == 252 || $t == 253) {
            $tn = 6; $n += 6; $noc += 2;
        } else {
            $n++;
        }
        if($noc >= $length) {
            break;
        }
    }
    if($noc > $length) {
        $n -= $tn;
    }
    $strcut = substr($string, 0, $n);
    $strcut = str_replace(array('&', '"', ''), array('&', '"', ''), $strcut);
    return $strcut.$dot;
}

PHP